Multi-tone signaling is an increasingly popular communication technique. During multi-tone signaling, a usable range of frequencies in a communication channel is divided into a series of frequency bands or sub-channels. Then, data, which is to communicated via the communication channel, is modulated using a transform operation and is subsequently up-converted using a group of carrier frequencies.
Multi-tone signaling becomes more effective as the number of frequency tones increases. However, the complexity of a communication system that uses multi-tone signaling increases with the number of sub-channels.
Furthermore, multi-tone signaling typically has high peak-to-average power ratio (PAPR). Unfortunately, high PAPR can reduce the efficiency of power amplifiers in the communication system. For example, if there is clipping in the power amplifiers, spectral re-growth (i.e., nonlinearities) will occur. Furthermore, while the PAPR can be reduced by adding redundancy (for example, additional power amplifiers), this redundancy will also increase the complexity and cost of the communication system.
Hence, what is needed are circuits and techniques which can be used in communication systems that overcome the problems listed above.
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